round() for float in C++

Question

I need a simple floating point rounding function, thus:

double round(double);

round(0.1) = 0
round(-0.1) = 0
round(-0.9) = -1

I can find

Answer 1

Best way to rounding off a floating value by "n" decimal places, is as following with in O(1) time:-

We have to round off the value by 3 places i.e. n=3.So,

float a=47.8732355;
printf("%.3f",a);